Recovery of rare-earth elements from nitrate solutions using polyethylene glycol 1500
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 7, pp. 1344—1348, July, 2020
Recovery of rare-earth elements from nitrate solutions using polyethylene glycol 1500* M. I. Fedorova,а Yu. A. Zakhodyaeva,а I. V. Zinov´eva,а and A. A. Voshkinа,b аKurnakov
Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninsky prosp., 119991 Moscow, Russian Federation. Е-mail: [email protected] bMIREA — Russian Technological University, 78 prosp. Vernadskogo, 119454 Moscow, Russian Federation
A new extraction system based on polyethylene glycol 1500 and NaNO3 was proposed for the recovery of light rare-earth elements (Ce, La, Nd, Pr, and Sm) from aqueous solutions. The equilibrium distribution coefficients and degrees of extraction of CeIII, LaIII, NdIII, PrIII, and SmIII in the proposed aqueous two-phase system were found. The dependences of the quantitative characteristics of rare-earth element extraction on the temperature, initial metal concentration, and acidity of the medium were obtained. The degree of extraction of the metal ions within one step was shown to exceed 60% at the phase ratio 1 : 1 without introducing additional complexation agents. Key words: liquid extraction, rare-earth elements, polyethylene glycol 1500.
Rare-earth metals (REM) are presently applied in manufacturing high-tech production, including lasers, electronics, computers, and others. For example, neodymium is used in the production of magnets, cerium is used in the production of catalytic converters for automobiles, lanthanum is applied in telescopic lenses and microchips, praseodymium is used in aviation engines, etc.1—4 Wide practical use of REM along with inefficient processing used components and materials results in the contamination of the environment with toxic metals.2 Owing to rush demand of REM and their high cost, increased attention is recently given to the use of secondary raw materials and, hence, it seems promising and urgent to develop methods for REM recovery from secondary raw materials of various types. The first stage of REM-containing waste processing is the leaching of the waste with mineral acids (hydrochloric, sulfuric, and nitric acid).5,6 In this case, REM are recovered nearly completely (~99%), but other metals are simultaneously transferred to the liquid phase.5,7 Oxalic acid was proposed for the use as a leaching agent in order to separate REM from other metals.6 Liquid extraction using neutral (tributyl phosphate (TBP), phosphine oxides), cation-exchange (bis(2,4,4-trimethylpentyl)phosphinic acid, di(2-ethylhexyl)phosphoric acid1,8), and anion-exchange extracting agents (Aliquat 336)8,9 diluted * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
with organic solvents (hexane, kerosene, xylene, and others) is widely used to separate the recovered metals.10,11 Tributyl phosphate is used for REM recovery from nitrate solutions 12 to form extracted complexes Ln(NO3)3•3TBP in the organic phase, and the
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